1. Field of the Invention
The present invention relates to a tapered roller bearing.
2. Description of the Related Art
Hitherto, there has been known a tapered roller bearing having an inner ring, an outer ring, a plurality of tapered rollers, and a cage. The inner ring has an outer peripheral surface formed as an inner ring raceway surface in the shape of a conical surface. The outer ring has an inner peripheral surface formed as an outer ring raceway surface in the shape of a conical surface, and disposed concentrically on the outer circumferential side of the inner ring. The tapered rollers are rollably disposed in an annular space between the inner ring raceway surface and the outer ring raceway surface. The cage has a plurality of pockets in which the tapered rollers are held. The tapered roller bearing is used to support a shaft mounted inside a gear mechanism such as a transmission and a differential device in an automobile.
Lubricating oil is distributed in such a tapered roller bearing by an oil drawing phenomenon called a pumping action of the tapered roller bearing. That is, lubricating oil is distributed by flowing into the tapered roller bearing from a cone front face rib (hereinafter referred to as a small rib) side, which is on a small diameter end portion side of the inner ring raceway surface of the tapered roller bearing, and being discharged from the a cone back face rib (hereinafter referred to as a large rib) side, which is on a large diameter end portion side of the inner ring raceway surface, because of a centrifugal force generated as the tapered rollers rotate and revolve. The pumping action is increased in proportion to the rotational speed of the bearing. Therefore, in the case where the rotational speed of the bearing in a transmission is high, the pumping action may be so strong that lubricating oil may not be delivered sufficiently to components such as bearings. In a differential device, lubricating oil stored in an oil reservoir is splashed and scattered by rotation of a differential ring gear, which is a component of the differential device, to lubricate the tapered roller bearing. In an initial period of rotation such as during startup of an engine, however, the splashing action of the differential ring gear may not be sufficient, which may cause poor lubrication. Because the conical surfaces of the tapered rollers in the tapered roller bearing contact the inner ring raceway surface through rolling contact, the temperature of the conical surfaces is not easily raised by sliding friction, and the conical surfaces are not easily seized. On the other hand, contact between the large end faces of the tapered rollers and the large rib that projects radially outward at the large diameter end portion side of the inner ring raceway surface is sliding contact. Therefore, in the case where the portion with such sliding contact is used under poor lubrication, the portion may be seized by a temperature rise due to sliding friction.
There is known a technology in which an annular guiding member that guides lubricating oil flowing toward an inner peripheral surface (outer ring raceway surface) of an outer ring, toward an outer peripheral surface of a large rib of an inner ring via a pocket of a cage, is mounted so as to be openable and closable via an elastic element at an end portion of the outer ring corresponding to a large rib side of the inner ring (an outer ring end surface of the outer ring on the large diameter side of the outer ring raceway surface) (Japanese Patent Application Publication No. 2008-232255 (JP 2008-232255 A)).
There is also known a bearing in which an end portion of an outer ring corresponding to a large rib side of an inner ring (an outer ring end surface of the outer ring on the large diameter side of an outer ring raceway surface), of the end surfaces of the outer ring, is formed to be thin and long, and an annular member with an L-shaped section is fitted into the inner peripheral surface of the end portion to provide a reservoir portion for lubricating oil (Japanese Patent Application Publication No. 2008-57791 (JP 2008-57791 A)).
With the technology according to JP 2008-232255 A, however, it is difficult to reduce the component cost since a plurality of components such as the annular guiding member and the elastic element are involved. For assembly of the tapered roller bearing, in addition, a three-in-one temporary assembly of the inner ring, the cage, and the tapered rollers may be fitted into the outer ring raceway of the outer ring with the outer ring press-fitted into a housing in advance. Therefore, the annular guiding member and the elastic element may present an issue in mounting workability in the case where the annular guiding member and the elastic element are mounted with the tapered roller bearing attached to the housing.
With the tapered roller bearing according to JP 2008-57791 A, the processability may be reduced by deformation or the like due to heat treatment because the end portion of the outer ring is formed to be thin. In addition, the annular member fitted into the end portion of the outer ring is pressed in the axial direction together with the outer ring when the outer ring is press-fitted into the housing, and therefore may be crushed by such a pressing force.